| Relative amounts of creep #161713 12/02/08 12:51 PM 12/02/08 12:51 PM |
Joined: Aug 2005 Posts: 2,921 Michigan PTP OP
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Posts: 2,921 Michigan | making a screecher and it has a luff pocket meant for wire but of course I am going to use line... and I have a question which one of these has the least amount of creep?
amsteel blue (dyneema sk-75, not "standard" spectra) vectran AS-78 technora (tech 12, ultratech, T-900)
No one seems to quantify creep (they quantify stretch but it is not the same) the amsteel is probably out due to high creep but thought I would throw it in there for discussion.
Secondly- if you pull the creep out- relatively easy to do- especially if it is tensioned like a halyard, does the line recoil when the tension is removed? I guess that would be stretch though... so then, theoretically if you get the creep out then it is out for good?
Last edited by PTP; 12/02/08 12:51 PM.
| | | Re: Relative amounts of creep
[Re: PTP]
#161733 12/02/08 04:02 PM 12/02/08 04:02 PM |
Joined: Oct 2005 Posts: 1,152 tampa, fl ksurfer2
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Posts: 1,152 tampa, fl | if you get the creep out then it is out for good? There's a joke in there somewhere....I just can't find it.
If your havin girl problems i feel bad for you son I got 99 problems but my beautiful wife ain't one | | | Re: Relative amounts of creep
[Re: ksurfer2]
#161734 12/02/08 04:05 PM 12/02/08 04:05 PM |
Joined: Dec 2005 Posts: 1,121 Eastern NC, USA tshan
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Posts: 1,121 Eastern NC, USA | What is the old saying?? "You can take the boy out of the creep, but you can't take the creep out of the boy...."
Something like that.....
Tom | | | Re: Relative amounts of creep
[Re: ksurfer2]
#161737 12/02/08 04:44 PM 12/02/08 04:44 PM |
Joined: Jun 2001 Posts: 12,310 South Carolina Jake
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Posts: 12,310 South Carolina | if you get the creep out then it is out for good? There's a joke in there somewhere....I just can't find it. Creep has a logarithmic relationship with time and loading. For all practical purposes, after a certain period of time, it does effectively go away when considering steel or synthetic rigging. You will be plagued with a good bit of creep early in the life of the rigging. It will not be of much concern some time later. Steel creeps much less than synthetic rigging but it does creep and stop. Creep (particularly in steel structures) can be beneficial by allowing highly localized (pin point) pressure areas to "creep" and deform slightly, without failure, to help distribute the high loading over a larger area.
Jake Kohl | | | Re: Relative amounts of creep
[Re: PTP]
#161739 12/02/08 05:09 PM 12/02/08 05:09 PM |
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Posts: 571 Hamburg | Hi PTP,
from my expierence with synthetic shrouds (sk75), I think initial creep is about 5%. I used them for half a year (mast up all the time), in the hope that the creep settles. However it found the shrouds to elastic in strong winds and got tired to retension the shrouds so often. In this time it doesn't settle. I think that one part of the creep comes from the braid and will affect any braided line. But it should settle after first use. In addition to that some materials like dyneema creep.
Creep does not recoil, by definition.
Actually I don't know about AS-78 and technora, but vectran was designed to have "no" creep (rumors say as towing line for sonars). You need about three times the diameter as the wire to get the same stiffness, if I remember right.
Not sure how your sail is rigged. Is a screacher a flat cut genaker or suoer sized jib? Normally you have the luff line attached to the head and tack shackles of the sail. In this case, the creep of the line means that the luff of your sail has to carry more load (the luff keeps its original length, the line gets longer). Then, increasing the halyard tension stretches the luff more than the line, which might be mean to your sail... However on land you can shorten the length of the line from time to time.
I am a lazy guy and resetting some line in sails keeps me from sailing. I would take a "non creep" line. Like polyester or vectran if you want to save 100g or so for some $$$ more.
Actually I have a "hooter" or screacher or whatever (a flat genaker...) and I use polyester as luff line.
Hope that helps.
Cheers,
Klaus | | | Re: Relative amounts of creep
[Re: PTP]
#161778 12/03/08 05:10 AM 12/03/08 05:10 AM |
Joined: Feb 2008 Posts: 242 Brisveagas Aido
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Posts: 242 Brisveagas | "What ever makes you happy... What ever you want.."
Dude you have to tell us what sort of boat you're putting it on. And im aware of the fact that its probably a Cat. The loads on the luff of an off the beach cat screecher would not be high enough to worry about creep in either poly or spectra or vectran.
Make it adjustable and you wont have to worry about it. Or get a qualified sailmaker to do it.
"i wish i was special.... your so f---ing special..."
Aido Viper 288
| | | Re: Relative amounts of creep
[Re: PTP]
#161789 12/03/08 09:39 AM 12/03/08 09:39 AM |
Joined: Jun 2003 Posts: 712 mikekrantz
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Posts: 712 | There' been entire volumes written onthis subject, but I'll try to summarize it.
It all depends on the size and loading percentage of breaking strength. If you're trying to maintain minimum diameter then wire is the way to go. If you're trying to save weight synthetic is the route.
Amsteel (sk75) is not appropriate for a luff wire unless you have a way to retension it - too much creep
Vectran has low creep, but has very low chafe and UV resistance - good for halyards, but not good for running or standing rigging.
AS-78 is an improved version of SK75, has excellent chafe and UV resistance, but still exhibits creep when loading at 60%+ of breaking strength.
Technora has low creep characteristics but absorbs moisture causing the fibers to swell. Once the fibers start swelling, it creates internal chafe within the braid and starts breaking down. You won't see it until the rope breaks, and it looks hollow on the inside.
There's a relatively new product out - Dynex Dux 75. They take SK75, heat and draw it through a die process. It realigns the chrystalyne (sp?) structure resulting in it being 40% stronger than SK75 and only having 3% creep at 90% load. 7mm Dux 75 weighs only 3.4 kg per 100 meters, and has a breaking strength 15,000 lbs.
Its pretty cool stuff, I've seen it used on ORMA 60's and Volvo 70's for standing rigging, strops, etc. I've used it to create backstays, inner forestays, and halyards for big monos.
Currently, I'm in the process of replacing all of the standing rigging on a R33 to reduce the weight aloft.
| | | Re: Relative amounts of creep
[Re: I20RI]
#161811 12/03/08 01:51 PM 12/03/08 01:51 PM |
Joined: Apr 2007 Posts: 291 JACKFLASH
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Posts: 291 | Small diameter vectran will fit your bill. Most vectran now has a coating for uv resistance but that is not an issue as it will be in the luff of the sail. As for abrasion vectran is strong in this department so no worrys there. I can tell you that pulling with small high tech line is interesting. I work at a car dealership and upon receiving a package from APS containing 5/32's vectran line and commenting on the breaking strength of the line I was told I was full of it. Money was wagered and we picked up the front end of a wrecked pickup truck by looping the line under the truck and then tieing it to the arms of a vehicle lift. The dry weight of a silverado is 4780lbs and we only picked up half the vehicle, but it was the heavy half with the engine.
Collin Casey Infusion Platform + C2 rig and rags = one fast cookie
| | | Re: Relative amounts of creep
[Re: I20RI]
#161819 12/03/08 02:50 PM 12/03/08 02:50 PM |
Joined: Feb 2008 Posts: 242 Brisveagas Aido
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Posts: 242 Brisveagas | Like Mike said Dynex Dux definetly still has creep. Lots of people claim it doesn't but in practice it does. Doesn't mean its not cool tho.
A double braid polyester luff line would be fine in the luff of a screacher for a small boat. Cheap and you wouldn't put enough load on it to stress it out too much.
How big is the Boat PTP?
Aido Viper 288
| | | Re: Relative amounts of creep
[Re: Aido]
#161821 12/03/08 02:53 PM 12/03/08 02:53 PM |
Joined: Jun 2001 Posts: 12,310 South Carolina Jake
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Posts: 12,310 South Carolina | I think he's talking about an F31.
Jake Kohl | | | Re: Relative amounts of creep
[Re: Jake]
#161826 12/03/08 03:05 PM 12/03/08 03:05 PM |
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Posts: 242 Brisveagas | Creep probably is an issue then. Any of the three or four PTP mentioned will do. Like i said it has to be adjustable. If its not you'll rip the sail in half. If you dont know what your doing you'll probably rip the sail in half any way.
Anti torque rope is what i would use so it can be furled and handled easily. It has relatively low creep too.
Who would've guessed a tri sailor on Catsailor.
Aido Viper 288
| | | Re: Relative amounts of creep
[Re: Aido]
#161828 12/03/08 03:25 PM 12/03/08 03:25 PM |
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Anti torque rope is what i would use so it can be furled and handled easily. It has relatively low creep too.
Who would've guessed a tri sailor on Catsailor.
I have a cat too. Dynex would be ideal but the smallest size it comes in is 9/32 which is too big, IMO, for the luff. My tri has 9mm dux shrouds which do exhibit some creep when it is setting (although hard to determine, more likely the splices settling than overt creep). What do you mean by anti-torque rope? | | | Re: Relative amounts of creep
[Re: PTP]
#161842 12/03/08 04:14 PM 12/03/08 04:14 PM |
Joined: Apr 2007 Posts: 291 JACKFLASH
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Posts: 291 | I don't remember if it is layline or APS but one of them I seem to recall offeres prestretching line, would that have the same effect at reducing creep? If so I might employee them to deal with my neighbor, talk about creeps.
Collin Casey Infusion Platform + C2 rig and rags = one fast cookie
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